Wk4 Ch17.5: Male Reproductive Anatomy

  1. 17.5 Anatomy
    • The male reproductive system includes the two testes, the system of ducts that store and transport sperm to the exterior, the glands that empty into these ducts, and the penis.
    • The duct system, glands, and penis constitute the male accessory reproductive organs.
  2. Inside penis
    • 3 cylindrical columns of erectile tissue
    • 2x corpus cavernosa (dorsal)
    • 1x corpus spongiosum (ventral)
    • The urethra runs through the middle of the corpus spongiosum.
    • The penis is highly highly vascularized and innervated.
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  3. Scrotum
    • Contain the testes
    • an outpouching of the abdominal wall and is divided internally into two sacs, one for each testis.
    • a sack of skin and superficial fascia that hangs outside of the body and houses the testes in two compartments.
  4. Testes
    • The male gonads. Responsible for making male gametes, sperm, and the androgen hormone testosterone.
    • During early fetal development, the testes are located in the abdomen; but during later gestation (usually in the seventh month of pregnancy), they usually descend into the scrotum (see Figure 17.2).
    • This descent is essential for normal sperm production during adulthood, because sperm formation requires a temperature approximately 2° C lower than normal internal body temperature.
    • Cooling is achieved by air circulating around the scrotum and by a heat exchange mechanism in the blood vessels supplying the testes.
    • In contrast to spermatogenesis, testosterone secretion can usually occur normally at internal body temperature, so failure of testes descent usually does not impair testosterone secretion.
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  5. Dartos muscle and cremaster muscle
    • dartos muscle: which is a smooth muscle visible at the bottom of this image contracts in the cold, wrinkles the scrotal skin, and thereby decreases heat loss.
    • The creamaster muscle: which is a skeletal muscle that runs the length of this mimetic cord also contracts in the cold, elevates the scrotum and testis as closer to the body.
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  6. Two tunics
    • Now the testes within the scrotum are surrounded by two tunics
    • The outer tunic is the Tunica vaginalis, which is derived from the peritoneum.
    • While the inner tunic is the tunica albuginea.
    • The tunica albuginea is actually a layer of fibrous connective tissue that covers the testes.
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  7. spermatic cord
    • The spermatic cord encloses these blood vessels, together with  the nerve fibres and lymphatics that supply the testes
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  8. Septa
    • fibrous septa project inwards from the tunica albuginea and subdivide the testes into lobules.
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  9. Lobules
    • testis is divided into about 250 sections called lobules
    • Which are tightly coiled with semineforous tubules
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  10. Spermatogenesis
    • Spermatogenesis is sperm formation
    • The sites of spermatogenesis (sperm formation) in the testes are the many tiny, convoluted seminiferous tubules
  11. seminiferous tubules
    • The sites of spermatogenesis (sperm formation) in the testes are the many tiny, convoluted seminiferous tubules.
    • The combined length of these tubes is 250 m (the length of over 2.5 football fields).
    • The seminiferous tubules from different areas of a testis converge to form a network of interconnected tubes, the rete testis (see Figure 17.9).
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    • These tubules are the sperm factories made out of a stratified epithelium surrounding a central fluid filled lumen.
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  12. Sertoli Cells
    • Found within seminiferous tubules and nourish developing sperm cells
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  13. Leydig cells
    • Secrete testosterone
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  14. Rete testis
    • The seminiferous tubules from different areas of a testis converge to form a network of interconnected tubes, the rete testis
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  15. efferent ductules
    Small ducts called efferent ductules leave the rete testis, pierce the fibrous covering of the testis (the tunica albuginea), and empty into a single duct within a structure called the epididymis (plural, epididymides).
  16. epididymis
    • Small ducts called efferent ductules leave the rete testis, pierce the fibrous covering of the testis, and empty into a single duct within a structure called the epididymis (plural, epididymides).
    • The epididymis is loosely attached to the outside of the testis. The duct of the epididymis is so convoluted that, when straightened out at dissection, it measures 6 m.
    • Sperm spend a few weeks here after testis to gain mobility.
    • This duct is full of microvili called stereocilia, which provide a huge surface area to help reabsorb some extra fluid and help pass along nutrients to feed the idling sperm.
    • Once through the duct they enter the inferior epididymis where they gain mitochondria to produce energy.
    • The epididymisdraining each testis leads to a vas deferens
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  17. Vas deferens
    • The epididymis draining each testis leads to a vas deferens (plural, vasa deferentia), a large, thick-walled tube lined with smooth muscle.
    • The vas deferens and the blood vessels and nerves supplying the testis are bound together in the spermatic cord, which passes to the testis through a slitlike passage, the inguinal canal, in the abdominal wall.
    • After entering the abdomen, the two vasa deferentia— one from each testis—continue to behind the urinary bladder base.
    • The ducts from two large glands (the seminal vesicles) which lie behind the bladder, join the two vasa deferentia to form the two ejaculatory ducts.
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  18. ejaculatory ducts
    • The ducts from two large glands (the seminal vesicles), which lie behind the bladder, join the two vasa deferentia to form the two ejaculatory ducts.
    • The ejaculatory ducts then enter the prostate gland and join the urethra, coming from the bladder.
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  19. Seminal vesicles
    • A pair of small hollow glands behind the bladder that secrete a yellowish slightly alkaline fluid that contains coagulating enzymes, fructose and other things to help nourish and transport sperm.
    • This fluid makes up 70% of semen.
    • It's slightly alkaline to help counteract the slightly acid environment both in the male urethra and the female vagina. 
    • These vesicle also secrete special prostiglandins that help increase sperm success outside the body by decreasing the viscosity of a female cervical mucous and actually triggering a reverse peristalsis in the uterus that help draw sperm up the female reproductive tract.
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  20. Prostate gland
    • The ejaculatory ducts then enter the prostate gland and join the urethra, coming from the bladder.
    • The prostate gland is a single walnut-sized structure below the bladder and surrounding the upper part of the urethra, into which it secretes fluid through hundreds of tiny openings in the side of the urethra.
    • The prostate gland encircles the urethra just inferior to the bladder.
    • During ejaculation, it contracts to squeeze its own special secretion into the urethra. It contains mainly citric acid and the enzyme PSA that helps keep semen liquified and thus easier to move and swim through.

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  21. bulbourethral glands
    • The paired bulbourethral glands, lying below the prostate, drain into the urethra just after it leaves the prostate.
    • Secrete a clear mucous that drains into the urethra to clear out any acidic urine prior to ejaculation
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  22. Semen
    • The prostate gland and seminal vesicles secrete most of the fluid in which ejaculated sperm are suspended.
    • This fluid plus the sperm cells constitute semen, the sperm contributing a small percentage of the total volume.
    • The glandular secretions contain a large number of different chemical substances, including
    • (1) nutrients,
    • (2) buffers for protecting the sperm against the acidic vaginal secretions and residual acidic urine in the male urethra,
    • (3) chemicals (particularly from the seminal vesicles) that increase sperm motility, and
    • (4) prostaglandins.
    • The prostaglandins in semen are thought to aid in sperm function and movement in the female reproductive tract.
    • The bulbourethral glands contribute a small volume of lubricating mucoid secretions.
Author
kirstenp
ID
352974
Card Set
Wk4 Ch17.5: Male Reproductive Anatomy
Description
Wk4 Ch17: Male Reproductive Physiology
Updated